Displacement-measuring optical device with orifice

Abstract

Micron-scale displacement measurement devices having enhanced performance characteristics are disclosed. One embodiment of a micron-scale displacement measurement device includes a phase-sensitive reflective diffraction grating for reflecting a first portion of an incident light and transmitting a second portion of the incident light such that the second portion of the incident light is diffracted. The device can further include a mechanical structure having a first region and a second region, the mechanical structure positioned a distance d above the diffraction grating and forming a wall of a cavity, the second portion of the incident light is reflected off of the first region of the structure such that an interference pattern is formed by the reflected first portion and the reflected second portion of the incident light. The device can further include an orifice formed in the cavity to provide for the passage of air between the inside and outside of the cavity.

1. A fabricated device comprising:
 a phase-sensitive reflective diffraction grating for reflecting a first portion of an incident light and transmitting a second portion of the incident light such that the second portion of the incident light is diffracted; 
 a mechanical structure having a first region and a second region, the mechanical structure positioned a distance d above the diffraction grating and forming a wall of a cavity, the second portion of the incident light is reflected off of the first region of the structure such that an interference pattern is formed by the reflected first portion and the reflected second portion of the incident light; and 
 an orifice formed in the mechanical structure to provide for the passage of air between the inside and outside of the cavity. 
 
   
   
     2. The fabricated device of  claim 1 , wherein the orifice is formed in the second region of the mechanical structure. 
   
   
     3. The fabricated device of  claim 1 , wherein the cavity includes:
 a side wall for positioning the mechanical structure at the distance d from the diffraction grating, the side wall comprising the orifice. 
 
   
   
     4. The fabricated device of  claim 3 , wherein another orifice for the passage of air between the inside and outside of the cavity is formed in the mechanical structure. 
   
   
     5. The fabricated device of  claim 4 , wherein the other orifice is formed in the second region of the mechanical structure. 
   
   
     6. The fabricated device of  claim 3 , wherein the orifice is formed in an outer region of the sidewall. 
   
   
     7. The fabricated device of  claim 3 , wherein the orifice is formed in an outer region of the sidewall. 
   
   
     8. The fabricated device of  claim 1 , wherein the orifice is formed in the second region of the mechanical structure. 
   
   
     9. The fabricated device of  claim 1 , further comprising:
 a substrate forming a wall of the cavity, and the orifice is formed in the substrate. 
 
   
   
     10. The fabricated device of  claim 9 , wherein the orifice formed in the substrate is not in the path of incident light directed through the substrate and toward the reflective diffraction grating. 
   
   
     11. The fabricated device of  claim 1 , further comprising:
 a controller coupled to said reflective diffraction grating for controllably adjusting at least a first feature of said reflective diffraction grating. 
 
   
   
     12. The fabricated device of  claim 11 , wherein said controller controllably adjusts the distance d between the diffraction grating and the mechanical structure. 
   
   
     13. The fabricated device of  claim 1 , wherein the orifice is formed during fabrication of the mechanical structure. 
   
   
     14. The fabricated device of  claim 13 , wherein the mechanical structure is microfabricated. 
   
   
     15. The fabricated device of  claim 14 , wherein the mechanical structure is formed by chemical etching. 
   
   
     16. The fabricated device of  claim 1 , wherein the orifice is formed in an outer region of the mechanical structure. 
   
   
     17. A device comprising:
 means for equalizing the air pressure between an inside and outside of a cavity, the cavity including a wall comprising a mechanical structure having a first region and a second region; 
 means for illuminating a reflective diffraction grating with an incident light, the diffraction grating being positioned a distance d from the mechanical structure, a first portion of the incident light being reflected and a second portion of the incident light transmitted through the diffraction grating such that the second portion of the incident light is diffracted; and 
 means for reflecting the second portion of the incident light off of the first region of the mechanical structure such that an interference pattern is formed by the reflected first portion and the reflected second portion of the incident light, 
 wherein the means for equalizing the air pressure comprises means for venting the air through an orifice formed in the mechanical structure. 
 
   
   
     18. The device of  claim 17 , wherein the means for equalizing the air pressure further comprises means for venting the air through an orifice in at least one wall of the cavity. 
   
   
     19. The device of  claim 17 , wherein the means for venting the air through the orifice includes means for venting the air through an orifice formed in the second portion of the mechanical structure. 
   
   
     20. The device of  claim 17 , wherein the means for venting the air through the orifice includes means for venting the air through an orifice formed in a side wall of the cavity, the side wall for positioning the mechanical structure at the distance d from the diffraction grating. 
   
   
     21. The device of  claim 17 , wherein the means for venting the air through the orifice includes means for venting the air through an orifice formed in a substrate, the substrate forming a wall of the cavity. 
   
   
     22. A microfabricated microphone comprising:
 a phase-sensitive reflective diffraction grating for reflecting a first portion of an incident light and transmitting a second portion of the incident light such that the second portion of the incident light is diffracted; 
 a substrate positioned below the diffraction grating; 
 a diaphragm positioned a distance d above the diffraction grating such that the second portion of the incident light is reflected off the structure to form an interference pattern by the reflected first portion and the reflected second portion of the incident light, the diaphragm including a sidewall adjoining the substrate such that the diaphragm and the substrate enclose a cavity; and 
 an orifice formed in the diaphragm to provide for the passage of air between the inside and outside of the cavity. 
 
   
   
     23. The microfabricated microphone of  claim 22 , wherein the orifice is formed during fabrication of the diaphragm. 
   
   
     24. The microfabricated microphone of  claim 23 , wherein the diaphragm is formed by chemical etching. 
   
   
     25. The microfabricated microphone of  claim 22 , wherein the orifice is formed in an outer region of the diaphragm. 
   
   
     26. The microfabricated microphone of  claim 22 , further comprising:
 a controller coupled to the reflective diffraction grating for controllably adjusting at least a first feature of said reflective diffraction grating. 
 
   
   
     27. The microfabricated microphone of  claim 26 , wherein said controller controllably adjusts the distance d between the diffraction granting and the mechanical structure.